Background. Previous research using a metaphorical anaesthesia monitor, where dimensions of rectangles proportionally represent 30 patient variable values, showed improved performance in diagnosing adverse events compared with the standard monitor. Steady-state values were represented by a frame around each rectangle. We developed a similar metaphorical anaesthesia interface, but instead of presenting four relatively simple complications, we presented 10 complications of various levels of difficulty. Our simplified monitor presented variables that anaesthetists and trainees suggested as being essential for diagnosis.

Methods. Thirty-two anaesthetists and anaesthesia trainees participated in the monitoring task. Three types of monitors were presented: standard monitor, metaphorical monitor, and metaphorical monitor with trend arrows emphasizing the direction of change. The subjects were presented with screenshots of the three monitor types displaying anaesthesia-related complications. They were asked to indicate treatment method and diagnosis for the displayed complication.

Results. No significant differences were found in time to diagnosis and accuracy between the metaphorical and standard monitor. There were also no differences between trend and no-trend monitors. Forty per cent of the complications were identified incorrectly.

Conclusions. Visual metaphors on anaesthesia monitors do not improve anaesthetists' performance in the operating theatre. Since all complications in this study were identifiable based on monitor values alone, it seems feasible to develop a decision support system (DSS) based on these values. We suggest that a DSS could support the anaesthetist by calling attention to diagnoses that may not be considered.